Abstract

The second-harmonic generation (SHG) has been one of the most intensively studied phenomena in surface and interface optics for the last decade due to its unique sensitivity to the structural and electronic properties of surfaces and interfaces of centrosymmetric media. A dc electric field breaks the inversion symmetry of the centrosymmetric semiconductor in the space-charge region (SCR) and induces the bulk dipole nonlinear polarization at the SHG frequency, which is governed by the cubic susceptibility. The relative simplicity of the description of the SHG response from Si(001) face originating from rotationally isotropic interfacial SHG response makes the Si(001)-SiO2 interface among the most important for investigation of fundamental aspects of the dc-electric-field-induced SHG (EFISH) phenomenon. The combination of bias dependences, azimuthal anisotropy of the SHG intensity, and the EFISH spectroscopy near the direct two-photon E1 transition of silicon allows us to fully deconvolve the field-induced contribution to the quadratic polarization and demonstrate the origin of the EFISH response. The experimental bias dependences of the EFISH intensity are shown to be more complicated functions than quadratic or linear dependence as it has been observed in earlier works and strongly depend on a doping concentration, an oxide thickness, the density of interfacial states, the fundamental and SHG wavelengths, silicon dielectric constants, etc. A systematic phenomenological model of the EFISH phenomenon is developed. Two main aspects of this model should be pointed out: (i) a detailed electrophysical model of the SCR with the accumulation and inversion regimes at the Si-SiO2 interface with account of the charged imperfections of the MOS structure as interface states and charged traps in oxide layer, which change the spatial field distribution in SCR; (ii) a rigorous nonlinear optical model of EFISH in SCR, which takes into account, using Green function formalizm, all retardation effects, absorption of the fundamental and SHG radiation, multiple reflection interference of both the fundamental and SHG waves in oxide film, and optical interference between field-dependent and field-independent contributions of the quadratic nonlinear polarization to the SHG field detected.

© 1998 Optical Society of America

PDF Article
More Like This
Dependence of optical second harmonic generation on electric field and strain at SiO2/Si(001) and Si3N4/Si(001) interfaces

J. I. Dadap, X.F. Hu, M.H. Anderson, M.C. Downer, J.K. Lowell, and O.A. Aktsipetrov
FD3 International Quantum Electronics Conference (IQEC) 1996

Fourth-harmonic generation at crystalline Si(001) interfaces

Y.-S. Lee and M.C. Downer
QFC1 International Quantum Electronics Conference (IQEC) 1998

Time-dependent electric field induced second harmonic signal at the Si/SiO2 interface.

W. Ndebeka, P. H. Neethling, C. M. Steenkamp, H. Stafast, and E. G. Rohwer
FW3A.46 Frontiers in Optics (FiO) 2012